Rear diff trouble


New Member
May 9, 2019
Farmington, mn
Last summer my girlfriend put my 04, automatic v6 mustang into revease in a neutral prank gone wrong. It killed the car on spot and I restarted it and drove it 2 blocks home and then parked it for the winter. I started it last week and drove about 20 ft. When it started grinding on turns from the rear and knocking real hard on occasion. I'm thinking the rear diff is the problem, but do not want to replace it if the trans or driveshaft took a big hit. I still have to pop the rear diff cover to see what's up. Any other ideas or views?
  • Sponsors(?)


SN Certified Technician
Aug 14, 2009
Houston Texas
Just wondering. What have you done to rule out something simple like bad U-joints?

If this were my car I would also be looking at the slip yoke. As well as all of the suspension points that might allow the axle to rotate the pinion up/down.

If it does turn out to be a problem inside the rear end itself almost anything wrong with a rear end (short of major breakage) can be repaired with a rebuild kit. The Ford rear end is a very "serviceable" unit.

I also thought the the transmission controller would not let an automatic go into reverse while going forward.

Have you considered the GF 2.0 upgrade? :)
Dec 30, 2018
Medford, OR
the GF 2.0 would definitely be your most cost effective way to go lmao :D

but I second starting at the simplest solution and working up from there. However if you haven't serviced your diff a fluid change can do wonders..... however not if you need a rebuild because then you would be doing the fluids anyways


New Member
May 9, 2019
Farmington, mn
Had the car up this weekend and rotated the rear axle, I can feel where the pinion and ring gear are damaged. No doubt that's is the issue.
Dec 30, 2018
Medford, OR
so now is the wonderful internal debate to get a rebuild kit, or if your taking them out then now would be a good time to change your gear ratio if you were thinking about it
Thread starter Similar threads Forum Replies Date
C Rear Diff Leak 1996 - 2004 SN95 Mustang -General/Talk- 4
BlazeKeeper GT rear diff in V6? 2005 - 2014 S-197 Mustang -General/Talk- 0
M 2012 V6 rear diff/axil whine only while turning 2005 - 2014 S-197 Mustang -General/Talk- 2
F rear end diff 1996 - 2004 SN95 Mustang -General/Talk- 16
M 2002 Mustang Rear Diff Side To Side Slack 1996 - 2004 SN95 Mustang -General/Talk- 1
Killa Solid Rear Diff Cover Fox 5.0 Mustang Tech 11
Bill Cool Suspension Control Arm Bushings = Rear Diff Bushings? Fox 5.0 Mustang Tech 19
Killa 85 Gt T5 Tranny Oil And 7.5 Rear Diff Oil Question Fox 5.0 Mustang Tech 4
D Rear End Makes Clunking Noise And Feels Loose, Grey Metallic Colored Diff Fluid SN95 4.6L Mustang Tech 2
S Rear Diff Questions SVT Tech Forum 1
G Drivetrain Rear Diff Noise 2005 - 2009 Specific Tech 2
J Rear diff poly - actual experience SN95 V6 Mustang Tech 0
V 8.8 Rear Diff Classic Mustang Specific Tech 8
stangman11 Noise From The Rear Diff Fox 5.0 Mustang Tech 18
pissedoff92 Is the factor weight on the rear diff necessary? Fox 5.0 Mustang Tech 22
BradleyMustang3 1997 Rear Diff. SN95 4.6L Mustang Tech 7
G Expedition - Rear Diff Bearing - Just Replace Diff? Other Auto Tech 0
R trans/rear diff leaks SN95 4.6L Mustang Tech 1
B need help, rear diff question.... 1996 - 2004 SN95 Mustang -General/Talk- 6
M fitting a 07 diff in a 04 rear??? SN95 4.6L Mustang Tech 4
R Rear diff fluid change SN95 4.6L Mustang Tech 5
russ1979 Help 8.8 rear diff., oil change Fox 5.0 Mustang Tech 3
COBRA90GT Which Permatex gasket maker for rear diff cover ? 1994 - 1995 Specific Tech 5
Killa How many quart of oil is T-45 and rear diff ? SN95 4.6L Mustang Tech 10
2001 greenGT what rear diff fluid 1996 - 2004 SN95 Mustang -General/Talk- 3
F 99 crown vic PI rear end/diff Fox 5.0 Mustang Tech 6
R 8.8 rear diff question Fox 5.0 Mustang Tech 10
4 what do i need to do installing a 8.8 disc brake rear diff? Fox 5.0 Mustang Tech 5
4 Rear diff leaking////will a 8.8 bolt to a reg 2.3 driveshaft? 2.3L (N/A & Turbo) Tech 1
T Rear Diff fluids 2005 - 2009 Specific Tech 8
RUNINAGT REAR DIFF?? 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- 1
T 06 rear diff 2005 - 2014 Specific V6 Tech 4
J Anyone else have problems with the rear diff. leaking? SN95 4.6L Mustang Tech 6
016erstang Rear Diff 1996 - 2004 SN95 Mustang -General/Talk- 2
4.6boy best rear diff and axles combo... SN95 4.6L Mustang Tech 12
mixedbreed02gt Cleaning up the rear diff housing and axles, what do i need? 1996 - 2004 SN95 Mustang -General/Talk- 0
6 How do you change the fluid in a 8" rear diff? Classic Mustang Specific Tech 10
M Changing rear diff fluid 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- 10
M No jacking on the rear diff. 2005 - 2009 Specific Tech 5
Killa what additives I need to put on my rear diff ? SN95 4.6L Mustang Tech 7
Killa What weight for my tranny and rear diff ? SN95 4.6L Mustang Tech 12
Killa rear diff whinning ? SN95 4.6L Mustang Tech 13
V rear diff going out? 1994 - 1995 Specific Tech 13
Mustang5L5 Changing rear diff friction mod needed with Mobil 1?? SN95 4.6L Mustang Tech 16
04sonicblueGT Rear Diff SN95 4.6L Mustang Tech 1
Night Shifter rear diff oil SN95 4.6L Mustang Tech 6
V 03 rear diff cover issues SVT Tech Forum 3
S Changed Rear End Diff fluid, now leaks? SN95 4.6L Mustang Tech 11
AdamantiumKnot What do I need for tranny/rear diff./gear fluid? SN95 4.6L Mustang Tech 6
nvrenuff 8.8 rear diff rebuild Fox 5.0 Mustang Tech 4
Similar threads